are you referring to a track day bike or track only bike? permanent track bikes are usually pieced together from salvage. all my track bikes were salvaged. therefore, no insurance is necessary.
track bikes are crash bikes. i don't recommend using your normal commuter, unless you have spare parts at hand. depending on the state, track (off road) bikes may be required to be registered.
your health insurance should cover unless it's explicitly written that it will not cover high risk activities (sky jumping, cliff diving, running with the bulls, etc..)
as for comp, it will cover it if you claim it as comp and not track damaged (need i further explain?)